Development of carbon nanotube bumps for ultra fine pitch flip chip interconnection

Since 1991, carbon nanotubes have been considered for successful applications in various fields due to their unique properties. In the present work, carbon nanotubes are applied in integrated circuit packaging, as the bump interconnection for flip chip. The reason for choosing carbon nanotubes as the bump material is their special electrical, mechanical and thermal properties, which may promote both the performance and reliability of the flip chip packaging. Moreover, carbon nanotubes can be formed according to a precisely predefined small-scale pattern, which makes extremely high density interconnection possible. Vertically aligned carbon nanotubes are grown on silicon in the form of square arrays of different sizes, heights and pitches. Attempts to use thermal compression and anisotropic conductive adhesive to bond chips carrying carbon nanotube bumps with ceramic substrates are also executed. Mechanical testing is performed afterward to determine the strength of the bonding interfaces. The strength of the bonding by thermal compression is very weak, in the range from 1.9 to 7.0 g/mm². The bonding by anisotropic conductive adhesive is much stronger, indicating a possible approach to bond chips carrying carbon nanotube bumps.